The present invention relates to a fuel valve injection valve for injecting fuel in an internal combustion engine, and especially to a technique suitable for preventing secondary fuel injection.
Japanese Patent Application Laid-Open Hei 1-1594060 discloses an electromagnetic fuel-injection valve for opening/closing an opening in a valve seat based on an ON/OFF signal having a duty which is determined by a control unit. In this electromagnetic valve, a magnetic circuit is composed of a yoke with a bottom part, a core with a plug part to fill the aperture of the yoke and with a cylinder extending through the core center line, and a plunger facing the core, separated by a gap. A spring is inserted inside the cylinder of the core, and the spring exerts pressure on a movable element of the valve, which is composed of the plunger, a rod, and a ball member, towards the face of the valve seat. The top part of the spring, on the side opposite the plunger, contacts the bottom part of a spring-adjuster inserted in the cylinder of the core, and adjusts the load set to the spring. A coil for exciting the magnetic circuit is wound around the outside of the core and inside the yoke. In the bottom part of the yoke, there is a plunger hole for admitting the plunger, along with a valve-guide hole to admit a stopper and a valve guide, which penetrates the bottom part of the yoke, and whose diameter is larger than that of the plunger hole. The stopper is provided to set the lift value (the stroke) of the ball-valve, and the thickness of the stopper is set so that the top of the plunger does not directly contact the bottom of the core when the movable element of the valve is pulled upward. On the rod, there is a stopping face which butts against the stopper. The valve guide is a housing for containing the ball valve, a fuel-swirl-flow generating element for applying a swirling force to the fuel, and on the rod, the stopping face of the rod; and a valve-seat face and a fuel-injection hole are also located at the bottom of the valve guide.
In the above-described conventional injection valve, only the spring is inserted between the bottom of the spring adjuster and the plunger.
In an electromagnetic fuel-injection valve (hereafter referred to simply as an injection valve) including the injection valves constructed according to the conventional technique, bouncing tends to occur when the stopping face of the rod butts against the stopper during the valve-opening operation, or when the valve element is seated on the valve-seat face during the valve-closing operation. If the bouncing occurs when the valve element is seated on the valve-seat face, a secondary fuel injection occurs after the intended injection, which in turn makes it difficult to accurately control fuel injection. Also, if the bouncing occurs when the stopping face of the rod butts against the stopper, this also makes it difficult to accurately control fuel injection. A structure which is able to suppress such bouncing has not yet been achieved.